Study Of The Inhibition Effect Of Cr⁶⁺/V⁵⁺ On Anammox Bacterial Activity

The anaerobic ammonium oxidation (Anammox) process is an efficient and environmentally friendly technology to treat waste water with ammonia; it has a lot of benefits including no need aeration, not producing warm gases and no need carbon source.However, this process has not been widely used in engineering due to its disadvantages, Anammox bacteria are very sensitive to environment and hard to get enriched. In addition, the heavy metals and carbon source in waste water are inhibitory factors, furtherly hinder the widespread application of Anammox process.In this essay, two kinds of heavy metals were investigated,Cr6+ and V5+.To investigate the inhibition effects of these two heavy metals on the activity of anammox bacteria, short-term and long-term inhibition experiments have been conducted. Also, the change of valence state in bio-reactor is investigated. Conclusions are as follows:(1) In short-term inhibition experiments, different concentration of Cr6+ and V5+ could exert different levels of inhibition on Anammox bacteria, leading to the decrease of nitrogen removal rate, hydrazine dehydrogenate activity and heme c concentration. The half inhibition concentration of Cr6+ is 2.847±0.012 mg-Cr6+/L, The half inhibition concentration of V5+ is 21.15±0.70 mg-V5+/L. In short-term recovery experiments, the inhibition of the heavy metals can both get recoverable, while the inhibition of V5+ can get completely recovered.(2) In long-term inhibition experiments, three levels of Cr6+ concentration exert different levels of inhibition of Anammox bacteria. All of the three levels can inhibit ammonia nitrogen removal efficiency, the inhibition is apparent in the first 5 days, but the reactor gets recovered later, the ammonia nitrogen removal efficiency of three reactors eventually gets 70%,70% and 68%?The inhibition to nitrite nitrogen removal efficiency is similar in three reactors. In the early days, with the increase of Cr3+ concentration, the nitrite nitrogen removal efficiency in all of the three reactors gets weakened. The nitrite nitrogen removal efficiency gets minimum at 13day.Later, the efficiency in all reactors get recovered.(3) The concentration of Cr3+ and nitrite nitrogen is highly similar in all reactors, it is inferred that Anammox bacteria can use Cr6+ as electron accepter to restore Cr6+.